Metal refining



Patented Dec. 5, 1933 1,937,650 METAL REFINING Harvey Nicholas Gilbert, Niagara Falls, N. Y., as

signer, dc Ncmours and Delaware by mesne assignments, to E. I. du Pont Company,

a corporation of No Drawing. Application May 9, 1931 Serial No. 536,309

8Claims.

This invention relates to the refining of metals, and more particularly to the treatment of alloys or other aggregation of metals to effect the removal of one or more of its lates specifically to removal of constituents such as calcium from copper alloys.

It is often desired to remove part or all of a metal constituent from an alloy. Small amounts of metals, which may be considered as impurities,

are frequently most undesirable. For instance, when copper is deoxidized by treatment with calcium, an excess of calcium is inevitably used and a small amount remains alloyed with the deoxidized copper. The removal of this residual calcium is important because its presence considerably decreases the electrical conductivity of the copper. Up to a concentration of 0.2%, each 0.05% of calcium reduced the conductivity of the copper approximately 1%. Small. amounts of calcium also increase the brittleness of the copper to a marked degree, rendering such copper less suitable for use as wire.

One method commonly used in metal refining consists in the formation of a slag in which the substance to be separated from the metal is dissolved. This slag is usually removed by mechanical means and frequently particles of occluded slag remain in the metal or alloy and impart undesirable properties. Metal removal by this method is also frequently incomplete and/ or diiiicult to control when it is desired to leave a definite small proportion of the alloying metal in the composition being purified.

This invention has as an object the partial or substantially complete removalof one or more of the metallic constituents of an alloy without slag formation. A specific object is the removal of substantiallyall of the calcium from a calcium-copper alloy. Other objects will appear hereinafter. I

My invention consists in heating the alloy to a temperature above its melting point and thenpassing through the molten alloy a gas which is substantially inert to the metal being refined but which is capable of reacting with the constituent or constituents to be removed to form volatile compounds thereof. By regulation of the time and temperature of treatment, the degree of agitation, the rate of gas flow, and the gases used, my invention may be used for the removal of a part, as well as substantially all..of one or more of the metallic conthe alloy. The degree of removal can be determined by analyzing the alloy remaining.

The following example illustrates the use of constituents and re-,

(or ws-ozl my process to 7 remove calcium from a calciumcopper alloy.

Example A'number of samples of calcium copper alloys containing definite amounts of calcium were melted and various gases melts for periods of five and thirty minutes each. The melts were analyzed for calcium before and after the gas treatment periods. drogen and ammonia were used, and were passed at from 1 to 10 liters a minute through the melt. The results are as follows:

Percent calcium otherwise forcing the unheated gas through the heated molten metal. The gas may also be preheated. The gas alone may serve to agitate, or mechanical agitation may be employed. In some cases it maysuiiice to simply contact the gas with the melt at its surface; vigorous mechanical agitationis then advisable. I

The proper temperature for the process and the rate of passing gas intocontact therewith will vary with the composition of the alloy, its I various characteristics and the amount and completeness of removal of constituents desired. It may sometimes be necessary to remove'one constituent to the desired extent with one gas and thereafter effect the removal of other constituents with another or other gases.

While my process has been particularly described with regard to removing calcium from copper it is also applicable to removing other alkaline earth metals, viz. barium, strontium and magnesium from copper alloys.

My invention as herein described possesses many advantages over prior methods used. By. this process, calcium is probably removed in a as metal vapor or perhaps as a vaporized calcium compound, and no objectionable product remains. The simplicity of this'method necessitates less equipment and results can be accomplished at a lower cost. Another advantage of this process is that a subvapor phase, perhaps passed through these Nitrogen,

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